Electric cable



Deb. 19, 1933. F. PALMER El AL ELECTRIC CABLE Filed June 18, 1951 I NVENTOR Frulzr iaK Palmer- Jiahn E. MAuliffl: BY /ATTORNEYS. ,8 I +9 I Patented Dec. 19, 1933 UNITED STATES PATENT OFFICE.

ELECTRIC CABLE New York Application June 18, 1931. Serial No. 545,172 6 Claims. (Cl. 173-287) This invention relates to improvements in electric cables especially of the type employing a flexible protecting armor.

One of the objects of this invention is to provide a cable construction which permits of the ready insertion of a; bushing between the paper wrapped insulated conductors and the end of the metal armor to protect the insulated conductors against abrasion.

A further object of this invention is the provision of a cable construction of this type which permits of the ready insertion of such a bushing.

A still further objectis to provide a cable which materially diiiers from standard cables by permitting the insertion of a bushing over the paper or other wrapping so that the methods oi facture need not be materially altered and the product is not rendered more expensive, while increased insulating properties are obtained.

Another object of this invention is the provision in a cable of this type of a paper wrap for the insulated conductors lying directly under the metal armor and applied in the form a longitudinal wrap with overlapping or abutting edges.

Another object is to provide a paper wrap of this type which is crimped so that it may be longitudinally stretched to provide a space for the insertion of the bushing.

A still further object of this invention is to provide a longitudinal paper wrap around insu lated conductors lying directly under the metal armor and arranged so that it may be torn oil even with the end of the bushing.

These and other objects as will appear from the following disclosure are secured by means otthis invention.

This invention resides substantially in the combination, construction, arrangement and relative location oi parts all as will be described in detail hereinafter.

Referring to the drawing Figure 1 shows an elevational view of the cable of this invention withthepaper wrap protrud ing beyond the ends of the armor;

Fig. 2 shows a vertical cross-sectional view through this cable with the paper wrap opened out ready to be torn oi! flush with the end of the inserted bushing:

Fig. 3 is an elevational view of the cable partly in section showing how the crimped paper wrap may be stretched longitudinally to permit the insertion of the bushing;

Fig. 4 is a view partly in elevation and partly 66 in section showing the relation of the parts after the bushing has been applied and the protruding-end oi the paper torn ofl;

Fig. 5 is an end elevational view of Fig. 4; and

Fig. 6 is an end elevational view of a modified type of cable with two longitudinal paper wraps having the abutting edges of the wraps diametrisally opposite each other.

In the use oi electric cables of the flexible armored type it is usual to remove the metal armor from the end of the cable for a short distance back irom the ends of the conductors to leave them exposed tor the purpose of mahng connections thereto. The metal armor is usually removed by cutting, sawing and the like, with the result that 79 a Jagged sharp edge is left which quickly wears through the insulated conductors at the point where they issue from the armor, weakening the electrical properties of the insulation on the individual conductors and often causing a. ground or direct short circirit. It is desirable, therefore,

to employ some form of protection for the insulated conductors at this point such as a bushing, for example, which may be inserted in the end of the metal armor surrounding the insulated conductors to cover or enclose the sharp edge of the armor.

Since the flexible metal armor which is wound around the insulated conductors grips them very tightly as required by the Fire Underwriters code it h rather difficult to provide suificient space for the bushing. Several constructions have been devised for this purpose but they all have disadvantages, among which is that of expense in construction and requiring alteration in established nufacturing methods. The cable of this invention includes a longitudinal paper wrap around the insulated conductors over which the metal armor is wrapped. Thus when the end of the armor is removed leaving the conductors with their paper wrap exposed it is easy to insert a bushing and tear off the exposed end oi the paper iiush with the end of the bushing. Due to the natural springiness of the metal comprising the armor it has been found that a bushing may then be inserted in between the paper wrap and the armor because the cut end of the armor expends sufficiently to provide this space. Further space is provided by means of this invention by employing crimped or wrinkled paper so that when the paper wrap is pulled longitudinally it stretehes and thins out leaving additional space which, together with the natural sprlnginess oi the severed end of the armor, pro- 110 vides adequate room for the insertion of a bushing around the paper.

All these features will be fully appreciated by direct and detail reference to the drawing. Such a cable is shown in Fig. l as comprising an outer wound flexible armor 1 made up in accordance with well known practice from a narrow preformed strip of metal wound into interlocking portions. This armor 1 is tightly wrapped about the insulated conductors 2 and 3 which are themselves enclosed within a longitudinal paper wrap 4 which has an abutting or overlapping seam 5 which runs substantially longitudinally of the conductors. The individual conductors may be of any suitable construction and comprise, for example, a copper wire core, a flexible rubber insulation and an outer fabric covering. The invention is not particularly limited to the form of these individual conductors. With the form of cable in Figs. 1 and 2 the end of the armor is cut off so as to leave the wires and paper wrap 4 projecting. The bushing may then be inserted between the paper and the end of the armor, and the paper is then torn flush with the edge of the bushing. Because of the natural springiness of the metal of the armor it will expand sufficiently under pressure to permit the insertion of the bushing. Such a cable with the bushing applied would appear, as indicated in Fig. 5, from the end thereof.

An additional feature of this invention is to provide a longitudinal paper wrap 4 which paper is crimped as more clearly indicated in Fig. 3. In this case the end of the projecting paper as indicated at '7, is grasped and pulled longitudinally of the cable to stretch it and thin it out a which action is aided by reason of the crimping or wrinkling of the paper. The reduction of the overall dimension of the paper wrapped insulated springiness of the end of the armor, is provided for the insertion of the bushing 8. The bush ing is slipped down over the end of the projecting conductors and paper wrap as indicated in Fig. 3 and forced down into place as also indicated in this figure. Fig. 4 indicates the appearance of the cable after the bushing has been applied and the projecting end of the paper wrap torn off. The thinning out of the paper wrap because of the longitudinal pulling is indicated also in this figure. The unstretched paper is indicated as having a greater thickness at 4' than it does at the end which projects through the bushing. Likewise the cable hasthis appearance from the end as illustrated in Fig. 5. If desired, as illustrated in Fig. 6 two longitudinal paper wraps, one It ing over the other, may be employed. Also, whereas the other figures show the paper wrap having overlying edges Fig. 6 shows the paper wraps having abutting edges. In the case of Fig. 6 the insulated conductors 2 and 3 are enclosed first within the inner longitudinal paper wrap 4 and are overlaid with a second longitudinal paper wrap 10 having its abutting edges diametrically opposite from the abutting edges of the inner wrap 4. As before, the paper wraps may be crimped and in this case even greater space is provided for the bushing because when both wraps are stretched longitudinally there is a greater reduction in overall diameter of the wrapped conductor.

The paper wrap may, of course, be treated in any suitable manner to be rendered moisture- 75 proof and/or flame-proof. Of course, paper used conductors is indicated in Fig. 3 showing how: adequate space, especially in connection with the in cables of this nature is naturally an insulator.

It will be seen from the foregoing that we have provided an armored cable which is capable of utilizing all of the advantages of employing a bushing for protecting the insulated conductor or conductors thereof from the severed edges of the metallic sheath. In addition thereto, however, we have provided an armored cable of this character wherein the moisture and flame-proofing as well as insulation at the severed end of the armor is not diminished. In fact, the insulation has been materially increased by the insulating property of the bushing. In the conventional armored conductor heretofore employed in connection with bushings of this type the insulation, moisture and flame-proofing properties at the point of severance of the armor have been greatly diminished due to the necessity of unwinding the spirally wrapped paper to afford sufiicient space to permit the insertion of the bushing.

It is of course apparent that the principles of this invention and the structure thereof may be equally well applied to -a cable having either one conductor therein or a plurality of conductors therein. It is intended therefore that the claims define the invention as applied to a single conductor cable or a multiple conductor cable. It is likewise apparent that the expression transversely crimped or the expression substantially transversely crimped as employed in the claims is intended to define any form of crimped or crinkled paper or other insulating strip which is so employed in the cable that when the wrap formed therefrom is subjected to a longitudinal pull the crimping or crinkling will unfold to reduce the overall thickness of the wrap to provide a space between it and the armor in which the bushing may be easily inserted.

From the above description it will be apparent that this invention resides substantially in certain principles which may be embodied in other physical forms than those illustrated in the drawing. We do not, therefore, desire to be strictly limited to this disclosure as given for purposes of illustration but rather-to the scope of the ap- 12 pended claims.

What we seek to secure by United States Letters Patent is:

1. An armored electric cable including an insulated conductor, a protecting covering for the conductor comprising a longitudinally wrapped substantially transversely crimped strip of fibrous insulating material, a flexible metal armor enclosing the whole, and a flanged bushing lying between the armor and the longitudinally wrapped strip, the bushing flange substantially enclosing the edge of the armor and the bushing shank occupying the space formed between the armor and strip by longitudinally stretching th strip to reduce its overall thickness.

2. In an armored electric cable an insulated conductor, a covering for the conductor comprising a strip of substantially transversely crimped insulating material, a metal sheath enclosing the whole and an insulating bushing lying between the sheath and the strip, said bushing being insertible by uncrimping the wrap of crimped insulating material by longitudinally stretching it.

3. An armored cable comprising a plurality of insulated conductors, an enclosing layer of Iongitudinally wrapped transversely creased insulating material, an outer metal sheath for the whole, and an insulating bushing lying between the wrapped conductors and the sheath in the space provided by removing the creases from the strin- 4. An armored electric cable comprising a plurality of insulated electrical conductors, a longito the seam oi the first wrap, a metal sheath enclosing the whole, and a bushing lying between the wrapped conductors and the sheath and abutting against the end thereof, the bushing Lying in the space provided when the wrapped layers are stretched lengthwise to uncrimp them.

6. An armored electric cable comprising a plurality o1 insulated conductors, an insulating strip ot transversely wrinkled paper surrounding the conductors and having a substantially longitudinal seam, a metal sheath surrounding the whole, and an insulating bushing lying between the paper layer and the metal sheath in the space provided when the wrinkled paper strip is stretched lengthwise to reduce the overall diameter of the wrapped insulated conductors.

FREDERICK PALMER. JOHN E. McAULIFFE. 

